The invention concerns a radar sensor that emits pulsed radiation for automobile applications. The invention also concerns a method for the production of such a radar sensor. Radar sensors of this kind are known in the art. Automobile applications such as radar sensors are usually used to assistant parking, to monitor blind spots, to anticipate accidents (pre-crashed sensing), for starting/stopping operation or during driving with distance monitoring, and/or to regulate separations (cruise control support).
Towards this end, differing sensors are normally used for monitoring the environment of the vehicle and for detection of remote objects, with these different sensors operating at different radar frequencies. For near field observations, high spatial resolution is important (with respect to separation as well as angle), whereas the angular information is less important for large separations.
For the monitoring of separations at large range, radar sensors are conventionally used having a frequency of approximately 76 Gigahertz. These frequencies have, however, the associated disadvantages that the short wave lengths in the microwave region cannot be used together with conventional components.
In contrast thereto, so-called ISM frequencies of approximately 24 Gigahertz are used for near field monitoring. These frequencies can be irradiated in a wide band fashion. A wide band signal is desirable, since the spatial resolution of reflected objects, i.e. the smallest possible separation with which two separate objects can be recognized as being separate, is improved with increasing band width. In order to further improve the bandwidth, the conventional radar sensors are generally operated in a pulse manner, since the signal bandwidth increases with shorter pulse width.
The conventional radar sensor has a planer, slot-coupled patch antenna, which can be excited via an associated aperture in a metallic, ground surface and via a dielectric dispose between the ground surface and the radiation surface. Excitation via a feed network to the radar sensor, results in the irradiation of electromagnetic waves. The conventional radar sensors have a length and width of several centimeters and a depth of approximately up to 3 centimeters, so that they can be integrated into conventional bumpers of motor vehicles.
With the assistance of a plurality of radar sensors, it is possible to detect objects throughout a wide angular region using the triangulation procedure. The directional characteristics of the radiating and receiving antennas are thereby adjusted in a geometric fashion with the assistance of the interference principal and also with the assistance of signal phase differences or with signal travel time differences using approximately 4 to 6 patches (radiation surfaces) at 3 db in an angular range from approximately 15 to 25 degrees in one direction and approximately 7 degrees in the other direction.
An advantage of the flat antenna structures compared to conventional antennas is that they are more economical to produce and they also result in a compact and light weight construction which can be built using standard components and which is easily integrated into circuits having micro-strip leads.
This economical principle is sufficient for small object detection ranges.
However, for larger separations of approximately 40 meters from the object, a relatively highly focused beam must be used, since ambient influences are otherwise excessive. Realization of such a strongly focused beam using a conventional planer antenna technology on the basis of the conventional interference principle would require a plurality of patches and are therefore a large amount of space. The antenna surfaces would then determine the size of the sensor and the size of future sensors would greatly exceed the size of current radar sensors.
Departing from this prior art, it is the object of the present invention to produce an economical radar sensor for automobile applications which, in addition to the detection of proximate objects, can also detect further removed objects while utilizing standard components and with one single radar sensor whose geometrical size is not substantially larger than the sizes of current conventional radar sensors.